Re: [MMUSIC] 10 BUNDLE questions

[Harald Alvestrand <[e-mail]>]

On 03/18/2013 04:59 PM, Justin Uberti wrote:
> You're looking at the handling of a=mid, not a=group.
>
> Section 9.2 indicates the handling of a=group, which seems to indicate 
> a subset is allowed:
>
>     A SIP entity that receives an offer that contains an "a=group" line
>     with semantics that are understood MUST return an answer that
>     contains an "a=group" line with the same semantics.  The
>     identification-tags contained in this "a=group" line MUST be the same
>     as those received in the offer, or a subset of them (zero
>     identification-tags is a valid subset).  When the identification-tags
>     in the answer are a subset, the "group" value to be used in the
>     session MUST be the one present in the answer.

Aha, I misinterpreted the phrase "BUNDLE mids in the answer doesn't match".

This is, in some sense, a subset of the question "is unbundling 
possible". I don't have a strong opinion on this.


>
>
>
> On Mon, Mar 18, 2013 at 12:08 AM, Harald Alvestrand 
> <[e-mail] <mailto:[e-mail]>> wrote:
>
>     On 03/18/2013 04:19 AM, Justin Uberti wrote:
>>
>>
>>>          1. If the BUNDLE mids in the answer doesn't match the
>>>             BUNDLE mids in the offer, what happens? (assume fail)
>>>
>>         I think this violates RFC 5888 section 9.1, so it should be a
>>         FAIL.
>>
>>
>>     According to 9.2, the only restriction is the answer mids must be
>>     a subset of the offer, so we would have to specify an exact match
>>     directly. But I think we do want to impose this restriction, or
>>     else we can't BUNDLE a new m-line until we know the other side
>>     wants to BUNDLE it as well.
>
>     The important phrase from 9.1 is
>
>        If a media stream that contained a particular "mid" identifier
>     in the
>        offer contains a different identifier in the answer, the
>     application
>        ignores all of the "mid" and "group" lines that might appear in the
>        session description.  The following example illustrates this
>        scenario.
>
>     So if there's any mismatch, we don't get BUNDLE negotiated.
>     Negotiation might not fail, but we don't get BUNDLE (or any other
>     form of grouping).
>
>
>